1) Technical Field
The invention relates generally to forming selective line-line interconnections, and more particularly to the use of additive solder processing to provide such interconnects.
2) Background Art
In the field of semiconductor processing, the use of a lead-tin solder to provide the interconnection between a metal lead from a mounted semiconductor chip and a card (or printed circuit board) is well known. In such processes, the board is coated with an epoxy or similar material upon which the lead-tin solder will not wet (a so-called "solder-phobic" material). Then a first mask is used to selectively remove the solder-phobic material from areas in which the solder is desired. Thus, when the solder is subsequently deposited by evaporation or otherwise, it will only wet in these selected areas.
In general, due to the ever-increasing sophistication of the memory and logic chips to be mounted on a given card, the card designer must have the flexibility to selectively alter the connections between the metal interconnect lines on the card that couple the card inputs to the leads of the mounted modules. In general, if a card designer is constrained to only build one interconnect line pattern for a given set of chip modules, he/she will quickly produce a large amount of cards that differ very minimally from one another. This is especially true in memory card design. For a given memory program, a number of different memory modules (ones with all arrays functional, versus ones with 3/4 of the arrays functional, versus ones with only 1/2 of the arrays functional) are produced. The goal of the memory card designer is to formulate a single card design that can accommodate the different pinouts associated with these modules, by providing different interconnect patterns on the card, without altering the configuration (or placement) of the interconnect lines themselves.
In the prior art, this was done by the use of "jumpers," which are discrete resistor devices of substantially zero ohms that are selectively bonded between the interconnect lines to be coupled together. In general, this is relatively time-consuming and inefficient process.
Accordingly, a need exists in the art for a simple structure and method for selectively providing connections between the metal interconnect lines on a card after the lines have been formed thereon.